Method and apparatus for threading yarn into a stretch and false twist crimping machine

ABSTRACT

A method and apparatus for threading a combination stretch and false-twist crimping machine having feed and draw rolls which continuously draw the yarn over an elongated heated plate and through a rotatable false-twist spindle, at least one movable guide means operating to place the running yarn in contact with the heated plate only after the false-twist spindle has first been adjusted to a speed substantially smaller than its normal operating speed, the movement of the guide means being such as to maintain a substantially constant yarn length between the feed and draw rolls and thereafter adjusting the false-twist spindle to its normal operating speed.

Unite 11.

States Patent 1191 Schippers 1 Oct. 22, 1974 METHOD AND APPARATUS FOR3,336,738 8/1967 Mattingly C181 57/34 115 YARN [NT A STRETCH AND3,541,775 11/1970 Fisher. Jr.

CRIMPINg MACHINE 3,559,255 2/l97l Cockroft 57/34 HS X 3,636,697 1/1972Treptow et a1. 57/106 [75] Inventor; Heinz Schippers, Rcmschcid,3,724,191 4/1973 Hooper ct a1 57/34 HS Germany LUSk Cl 3,733,801 5/1971Jones [73] Assignee: Barmag Barm r M hin nf k 3,747,227 7/1973 22mg eta] 57/106 x Aktiengesellschaft, Wuppertal, Germany Primary Examiner lohnPetrakes 22 Filed; 2 1972 Attorney, Agent, or FirmJohnston, Keil,Thompson & Shurtleff 1211 Appl. No.: 303,086

[57] ABSTRACT [30] Forelgn Apphcatmn Pnomy Data A method and apparatusfor threading a combination Nov. 9. 1971 Germany 2155514 Stretch andfalse twist crimping machine having feed and draw rolls whichcontinuously draw the yarn over [52) US. Cl 57/34 HS, 28/62, 57/106, anelongated heated plate and through a rotatable 57/157 TS false-twistspindle, at least one movable guide means 1 it. p ti g t pl th i g y i tt th [58] Fleld of Search 57/34 5565 157 T5, heated plate only after thefalse-twist spindle has first 57/157 90, 106; 28/62 been adjusted to aspeed substantially smaller than its normal operating speed, themovement of the guide 1 1 References Cited means being such as tomaintain a substantially con- UNITED STATES PATENTS stant yarn lengthbetween the feed and draw rolls and 2,780,047 2 1957 Vandamme C111157/34 HS thereafter adjusting the false-twist Spindle to its 2,918,77812 1959 Wormser 57/34 HS mal operating speed. 3.041.813 7/1962Enneking.... 57/34 HS 3,289,400 12/1966 Scragg 57/34 HS 11 Clam, 8Drawmg PATENTED 2 21974 mi 11: a

FIGI

METHOD AND APPARATUS FOR THREADHNG YARN INTO A STRETCH AND FALSE TWISTCRIMPING MACHINE False-twist crimping machines consist essentially of afeed means for the continuous delivery of a yarn taken off a supplyspool and a heating device as well as a false-twist assembly and a drawmeans to at least maintain the yarn under a certain tension. After thedraw means, the yarn may be subjected to a second heat treatment and/orwound into a durably crimped product on a take-up spool or the like. Theapplication of heat to the yarn has been carried out with contactheating devices and also with convection heating apparatus. The falsetwisting is accomplished by means of a rapidly spinning false-twistspindle or by means of friction between the running thread and rotatingwheels, drums or similar elements. The initial yarn being delivered ismost usually already in the form of a stretched yarn. The servicing offalse twist machines occurs randomly, i.e. each operating position of amulti-unit machine is serviced as needed while the other positionscontinue to function.

For economical and technical reasons, it has become especially desirableto also undertake a stretching of a multifilament yarn on the samemachine used for imparting a durable false-twist or so-called torquecrimp. In this case, the machine is used for processing an unstretchedsynthetic thermoplastic yarn, e.g. such as polyethylene terephthalateyarn. in one version of this combined apparatus for stretching andfalse-twist crimping, an additional feed mechanism is introduced priorto the feed rolls leading into the heating device. The relative speedsof these two feed means are then adjusted in such a manner that the yarnis stretched by a predetermined amount before being conducted to theheating device. (For example, see German Patent No. 1,807,687.)

The present invention is particularly concerned with yet another versionof such a combined stretching and false-twist crimping machine whereinthe stretching occurs simultaneously with the crimping. This isaccomplished by adjusting the relative speed as between the draw rollsor similar transporting means following the false-twist assembly and thefeed roll or similar feed means preceding the heating device so that astretching occurs simultaneously in the same step or stage as thefalse-twist and heat treatment of the yarn. (For example, see BritishPatent No. 777,625.)

It is especially difficult to achieve a satisfactory threading of theyarn into the individual working positions of this last mentionedcombination stretch and false-twist crimping machine. The threadingoccurs while the many other working positions are in operation. For thisreason, it is not possible to shut off the heating device, which iscentrally controlled and regulated, when threading a single position.This means that the stationary or only slowly running unstretched yarnmaterial comes into direct contact with the heating device while it isstill at the high operating temperature. Depending upon the yarnmaterial, this in turn leads to yarn breakage, embrittlement or meltingof the unstretched thermoplastic filaments. Polyester yarns or threadsare especially sensitive to heat in their unstretched state.

It is a primary object of the present invention to provide a method andcertain apparatus which will avoid prior problems in the threading andoperation of a combination stretch and false-twist crimping machine.More particularly, it is an object of the invention to thread aheat-sensitive but initially cold and unstretched polyester yam into acombination stretch and false-twist crimping device in a rapid andcontrolled manner without any substantial damage to the yarn orexcessive loss of production time.

It has now been found in accordance with the invention that these andother objects can be achieved in threading an apparatus for thesimultaneous stretching and false-twist crimping of a yarn composed ofsynthetic thermoplastic filaments wherein the yarn is continuouslyconducted for stretching in a normal operating path between a stretchfeed point and a stretch draw point while simultaneously being subjectedto a heat treatment by direct contact with an elongated heating surfacein said normal operating path and also imparting a false twist to theheat treated yarn by means of a rotating false-twist spindle before theyarn reaches said stretch draw point, provided that the process includesthe steps of first threading the yarn from the stretch feed point to thestretch draw point through the false-twist spindle and also through amovable guide point adjacent one end of the elongated heating surface,this guide point being initially maintained in a position such that theyarn runs in a preliminary operating path which is free of contact withthe heating surface, then conducting the yarn through said preliminarypath while adjusting the speed of the false-twist spindle to a speedsubstantially smaller than its normal operating speed, thereafter movingthis guide point to bring the yarn into its normal operating path incontact with the heating surface, the movement of the guide point beingsuch that the yarn length between said stretch feed point and saidstretch draw point remains substantially constant and subsequentlyadjusting the false-twist spindle to its normal operating speed. Thisimproved method according to the invention is especially applicable tothe proper treatment of unstretched polyethylene terephthalate filamentsor yarns as the initial material being treated.

The known combination of apparatus essentially includes spatiallyseparated feed roll means and draw roll means for stretching a length ofyarn therebetween, an elongated curved heating plate for contact withthe yarn being stretched and positioned to receive the yarn from saidfeed roll means during normal operation and a false-twist spindlefollowing said heating plate for imparting a temporary twist to the yarnat a point preceding said draw roll means. The improvement of thisapparatus in its broadest context accordingto the invention includes atleast one yarn guide means adjacent one end of the elongated heatingplate for movement substantially perpendicular to the plate from an openposition in which the yarn is maintained free of contact with the plateto a closed position in which the yarn is maintained in running contactwith the plate, the movement of the guide means between said open andclosed positions being such that the yarn length between the feed rollmeans and the draw roll means remains substantially constant.

Particular yarn guide means in a number of combinations with the stretchand false-twist crimping apparatus are illustrated by the embodimentsshown in the accompanying drawing wherein:

FIG. 1 is a schematic side elevational view of one embodiment of theinvention in which a feed godet or set of feed rolls is itself movableto act as the essential yarn guide means for threading the combinationstretch and false-twist crimping machine;

FIG. 2 is a schematic side elevational view of another embodiment of theinvention in which the movable yarn guide means is positioned above acurved heating plate traversed twice by the running thread;

FIG. 3 is a front plan view of the same embodiment shown in FIG. 2;

FIG. 4 is another schematic front plan view of a contact heating plateadapted to receive a plurality of running yarns with several traversingruns each across the plate and with reversal elements above and belowthe plate as the movable yarn guide means;

FIG. 5 is a schematic perspective view of yet another embodiment of astretch and false-twist crimping machine with a curved and slottedheating plate for a doubly traversing yarn path and at least one movablereversing element as the essential yarn guide means for threading theapparatus; and

FIGS. 6, 7 and 8 illustrate schematic cross-sections of suitablyenclosed heating zones where the contact heating plate is arranged nearthe upper end of the stretch and false-twist machine so as to requirespecially adapted movable yarn guide means for threading the machine ata point which is normally out of reach of the person tending themachine.

In all of the illustrated embodiments of the apparatus or combination ofthe invention, there is at least one yarn guide element or assemblywhich is movable in a path substantially perpendicular to the verticalplane of the heating plate while the yarn is fully engaged and runningin the stretch and false-twist apparatus first out of contact with theheating plate and then in running contact with this plate. Mostimportantly, this perpendicular movement, which is subject to slightvariation for obvious reasons, must occur while essentially maintaininga constant yarn length between the feed and draw means used forstretching the yarn.

Referring to the first embodiment of the invention as shown in FIG. 1,the stretch and false-twist crimping machine generally requires a spoolholder to carry the supply spool l of unstretched polyester yarn Y whichis cold" in the sense that it is provided at room temperature andwithout any special heat treatment as it is fed into the machine. Eachprocessing position or unit of the machine also includes a feedmechanism 2 and a pair of draw rollers 3 or the like which can becontrolled or regulated at different feed and draw speeds by anyconventional control system 4 to stretch the yarn over the lengthbetween the nip points, i.e. so as to adjust the speed ratio between thefeed point and draw point where the yarn is clamped or engaged inrunning contact with the feed and draw means, respectively.

Two fixed guide eyelets 5 and 6 direct the yarn Y in a normal operatingpath for contact with the slightly curved surface of heating plate 7having an inlet 7a and outlet 7b for circulation of a heating medium.The feed mechanism 2 itself is movable in a slightly curved path on asuitable track or guide rail as indicated by the double headed arrow sothat it can be placed in a closed position 8 for normal operation of themachine or in an open position 9 for initial threading of the unit inaccordance with the invention.

Thus, while the feed means 2 is in its open position 9, the yarn istaken from the supply spool 1, through eyelet 5 and engaged in the feedmeans 2 at its outermost or open position 9 opposite the bottom end ofcontact heating plate 7 and then taken through eyelet 6 adjacent the topof the plate 7 to be engaged with the false-twist spindle ll operated bydrive belt 12. The draw rolls 3 finally engage the yarn Y above thespindle 11 so that the yarn is continuously conducted through theapparatus and taken up onto a conventional winding package (not shown).

The threading of the yarn thus occurs while the feed mechanism as amovable guide means keeps the yarn out of contact with heater 7 withoutotherwise interfering with the essential threading and engagement of allother yarn-conducting or yarn-twisting elements of the apparatus. Oncethe spindle 11 is brought to a speed substantially smaller than itsnormal operating speed, the feed and guide means 2 is moved back intoits closed position 8 to quickly engage the running yarn Y with thecurved heated surface of plate 7. Only then is the false twist spindlell brought up to its normal operating speed.

Thus, the contact heating plate 7 can be maintained at the normaloperating temperature to receive a number of yarns in a correspondingnumber of stretch and false-twist crimping units of a single machine.The initially threaded yarn of any given unit being placed in operationis preferably continuously drawn or stretched between the feed and drawpoints but with the false-twist spindle 11 only lightly engaged, i.e. inrelatively loose frictional contact with drive belt 12, so that theinitial revolutions of this spindle take place at a rate far belownormal operating speed, eg more than about 20 percent and preferably20-50 percent smaller than this normal operating speed. Then, the speedof the spindle can be increased up to full normal operating speed afterthe yarn is brought into contact over the entire length of the plateheating surface.

This procedure of the invention offers the advantage that only therunning and stretched yarn, which is thus temperature sensitive, isapplied onto the contact heating plate. On the other hand, however, themovement of the yarn from its preliminary threading path into its normaloperating path on the heating plate can lead to an excessive tensionwith yarn breakage or to a reduction in stretching with a melting of theyarn on the heating plate. Also, the low speed of the false-twistassembly during the initial threading stages causes a very favorablefrictional relationship for the running yarn and tends to avoidexcessive tension on the yarn. The method of the invention permits amore certain and rapid threading of the yarn within an optimally shorttime and with a minimum of yarn breakage.

In referring to a substantially perpendicular movement of the essentialyarn guide means of the invention, it should be understood that this istaken with reference to a substantially flat surface of the elongatedheating plate. In fact, this plate preferably has a slight curvature andthe movement of the yarn guide means in and out of the normal operatingposition preferably occurs in a path which represents an involute to thecurved surface of the heating plate.

Thus, the path of the feed and guide means 2 represented by thedouble-headed arrow in FIG. 1 is essentially perpendicular to butpreferably an involute of the curved contacting surface of the heatingplate 7. Then,

in moving between the positions 8 and 9, any change in the length of theyarn path between the feed means 2 and draw means 3 is substantiallyprevented. Thereby, variations of yarn tension are avoided which cancause breakage through excessively high tension or a melting of the yarnon the heating plate when tension becomes too low.

The particular stretch and false-twist crimping machine shownschematically in FIGS. 2 and 3 has a stretching zone formed between thespeed regulated feed rolls 2 and draw rolls 3 which in this instance areplaced below the heating plate 7 with its gilft 7a and outlet 717 forthe fluid heating medium This permits the yarn Y to pass twice over theheated curved surface of the plate 7, e.g. somewhat at an angle asindicated in FIG. 3. In this overall stretching zone, one can furtherprovide another heating device such as the stretch pin 13, preferablybetween the feed rolls 2 and the heating plate 7'.

In this instance, the yarn Y is conducted from the feed rolls 2 upwardlyover the heated surface 7', preferably with preheating by wrapping aboutonce around the fixed heating pin 13, and is then reversed to travelback downwardly again over the heated surface 7 by means of the guide ordeflecting member 14 arranged close to the upper end of the contactheating plate. The yarn Y then is taken off through the fixed eyeletguide 10 and the false-twist assembly 11 to the draw rolls 3'. Bysliding the deflecting member 14 back and forth on the guide rail 15between the open position 8' and the closed position 9', the yarn y ismaintained out of contact or placed in contact with the curved surfaceof the heated plate 7. The rail or track 15 is placed in such a manneras to be approximately perpendicular to the plate 7', i.e. so that themovement of the deflecting member 14 changes the yarn length between thedraw and feed rolls only very slightly. Again, the perpendicularmovement of the member 14 as a yarn guide means is essentially withreference to a plane tangential to the curved surface of the heatingplate 7'. Also, while the guide rail 15 is shown to be straight, it canalso be formed as an involute to the surface of the contact heatingplate or as an arc of relatively large radius. Other minor variations inthis structure or the arrangement of the movable yarn guide means arequite acceptable, provided they meet the requirement of maintaining theyarn length in the stretching zone between the feed and draw points.

In FIG. 4, the yarn guide means are selected and arranged in such amanner that the yarns Y and Y" are conducted three times over thecontact heating plate 7 which is substantially the same as the plate inFIGS. 2 and 3. Thus, each deflecting member 14a, 14b, 140" or 14b isconstructed and mounted on a guide rail in the same manner as the member14 in FIG. 2 so that every run of yarn across the face of the plate 7'can be moved into or away from contact with the heated surface of thisplate. Again, the stretching carried out simultaneously with the falsetwist imparted by the spindle means 11 or 11" can be accomplished bymeans of adjusting the relative speeds of the paired feed and draw rolls2'3 and 2",3". As illustrated in this example, one can further carry outa preliminary stretch between a prior set of feed rolls l6,l6 and thecorresponding subsequent feed rolls 2',2". Each pair of rolls l6',2 and16",2" has a heated stretch pin 17' and 17" respectively associatedtherewith to provide sufficient heating of the yarn in this preliminarystretching zone. All such paired rollers for the stretching of the yarnare easily regulated for adjustment of the amount of stretch by anysuitable control means such as that indicated by the numeral 4 in FIG.1.

The stretch and false-twist crimping arrangement shown in FIG. 5 isespecially advantageous in providing two parallel passes of the yarnover and in contact with the preferably grooved surface of the heatingplate 18. In this instance, a single fixed deflection member 19 islocated below the heating plate 18 while another fixed guide 20 issituated directly after the feed means 2 such that the incoming yarn Yis placed in parallel alignment with the outgoing yarn Y being conductedto the false-twist assembly 11 and draw means 3. One or two movable yarnguide members 21 and 22 are positioned above the plate 18, for exampleto provide a means of changing the yarn path by moving guide rod 21 in atrack 23 from the normal operating position 8 to a position 9" where theyarn is maintained free of contact with the heated plate 18. The use oftwo guide rods 21 and 22 is of particular value in this embodimentbecause both rods can be jointly manipulated through predetermined pathswhich keep the total yarn length substantially constant for thestretching zone between the feed means 2 and draw means 3. Such paths ofmovement of rods 21 and 22 can be straight, an arc with a large radiusor an involute to the grooved and curved yarn contacting surfaces of theheated plate 18. At least one of these guide rods 21 must follow a pathwhich is approximately perpendicular to the plate while the other guiderod 22 may follow a parallel path or one extending in the same directionto maintain a constant yarn length or it may follow a path extending ina different direction. For example, rod 22 can travel upwardly while rod21 is moved outwardly from position 8 to position 9". This is mostadvantageous in providing a definite parallel arrangement of the ingoingand outgoing yarns Y and Y within a relatively compact space.

The embodiments shown in FIGS. 68 are particularly preferred if thecontact heating plate is to be located in the upper portion of themachine such that it is out of normal reach of anyone tending themachine. Stretching occurs in the yarn path extending from the feedrolls 2 to the draw rolls 3, the yarn passing twice over the heatedplate 7 as in FIGS. 2 and 3.

The apparatus of FIGS. 6-8 is also characterized by the fact that theheating plate 7 is maintained in an at least partly enclosed box orcasing to provide heat insulation and a certain degree of protection forthe transported yarn. Therefore, it is essential under these conditionsto provide a means of positioning the thread at a remote and relativelyinaccessible location, for example near the upper end of the at leastpartly enclosed heating plate. This positioning means essentially takesthe form of an extension rod 24 with a suitable handle 25 formanipulative movement of the thread upwardly mounted in a holder 29(FIG. 8) but is generally introduced so as to slide upwardly in aposition which is essentially parallel to the thread contacting surfaceof the heated plate 7'. At its upper end, the rod 24 carries a yarnguide element 30 which serves to receive the incoming yarn from thestretch feed means 2 as the yarn extends past or in contact with theheating plate 7' and then directs the yarn back again over the plate tothe false-twist spindle l1 and then to the stretch draw means 3.

The rod 24 can be placed in a lowered position 24' so that the persontending the machine can reach the guide element 30' near the bottom endof the heating plate 7 for initial insertion of the yarn. The rod isalso capable of being fastened in a second position 24" where the guideelement 30 retains the yarn ina path free of contact with the heatingplate 7.

In FIGS. 6 and 7, the yarn guide element 30 is connected to a lever 31or 32 which pivots on the axis-33. In threading the yarn and sliding therod 24 into the second position 24", the lever 31 is locatedapproximately parallel to the rod, i.e. in a retracted or withdrawnposition. However, when further sliding the rod 24 from position 24 intoan immediately adjacent third position 34, the lever 31 or 32 isactuated by a boss or projection 35 or 35' extending from the casing 27or 27' so as to pivot the lever and its guide element 30 into anextended or expanded position 36. This extended position is maintainedby locking the arm 24 in its third position by any suitable clamping orlocking mechanism (not shown) so as to provide a firm support for theguide 30 and its lever 31 or 32. Any number of variations in theconstruction of this lever are feasible, for example using a two-armedlever 31 as in FIG. 6 or a single-armed lever 32 as in FIG. 7. Whenusing this latter single-armed lever, it is preferable to maintain orresiliently urge the lever 32 into its parallel position by means of atorsion spring 37. Then, when the rod 24 is lowered to disengage thelever 32 from the boss 35', the lever automatically returns to itsretracted position parallel to the rod.

In the embodiment of FIG. 8, the yarn guide element 30 is rigidlyconnected to the end of the rod 24 on an axis slightly inclined from aperpendicular to the rod axis. The rod in this case can be pushed to itssecond position 24" in which the guide element 30" at this position islocated in the upper region or above the contact heating plate 7 at adistance sufficiently far away to maintain the guided yarn in a pathfree of contact with the heating plate. The rod 24 is pivotable with themember 29 so that the guide element can move to the position 36 and therod and guide assembly clamped or locked in this position formaintaining the yarn in its normal operating path in contact with theheating plate 7.

In all of these embodiments, it is still essential to provide a movementof the upper yarn guide element 30 from its open position 30" to itsclosed position 36 in a direction approximately perpendicular to theheated yarn contacting surface of plate 7 or preferably in a swingingare which is as close as possible to the involute curve of the slightlycurved surface of the heating plate.

The particular embodiments of FIGS. 6-8 are especially advantageous andmost useful where it is desirable to locate the heating plate within achamber 28 which is almost fully enclosed on all sides and provided withheat-insulated walls by the box or casing 27'. The only opening 38 isthat required for introducing and withdrawing the yarn, using an openingsufficiently large to also permit a complete withdrawal of the guideelement 30 externally of the casing 27' so that the yarn can be insertedthereon.

In special embodiments such as FIGS. 6-8 which require an initialapplication of the yarn onto the guide element 30, eg at a point belowthe heated plate 7 and/or externally of the casing 27', it will beapparent that the method of threading according to the invention willrequire a preliminary step of lifting the movable yarn guide 30 into itsupper or second position 30" before the yarn is brought through thefalse-twist spindle 11 and then to the draw means 3. Thus, the yarn isalready in position 30" when the stretching effect of the feed and drawmeans is placed into operation while the false-twist spindle is operatedwell below its normal operating speed. Only then is the rod 24 pushedinto the third position 34 so thatthe yarn guide element swings on oneof the lever arms or pivots on the rod into its normal operatingposition 36, the spindle ll thereafter being brought to its normaloperating speed.

Although some variations of the yarn length between the stretching feedand draw means are permissible, they are preferably limited to somethingless than 1 percent and preferably less than 0.1 percent of thisstretching zone length. It will be apparent that this order of magnitudeis attainable within the limitations of structure and position of theessential elements of the new combination. The use of this combinationin a stretch and false-twist crimping machine greatly facilitatesthreading of the yarn so as to reduce the labor and expense of tendingsuch a machine. Also, a continuous supply of a high quality stretchedand torque-crimped yarn is obtained with a minimum of waste or poorquality yarn.

The invention is hereby claimed as follows:

1. A method of threading an apparatus for the simultaneous stretchingand false-twist crimping of a yarn composed of synthetic thermoplasticfilaments wherein the yarn is continuously conducted for stretching in anormal operating path between a stretch feed point and a stretch drawpoint while simultaneously being subjected to a heat treatment by directcontact with an elongated heating surface in said normal operating pathand also imparting a false twist to the heat treated yarn by means of arotating false-twist spindle before the yarn reaches said stretch drawpoint, which process comprises:

first threading the yarn from said stretch feed point to said stretchdraw point through said false-twist spindle and also through a movableguide point adjacent one end of said elongated heating surface, saidguide point being initially maintained in a position such that the yarnruns in a preliminary operating path which is free of contact with saidheating surface;

then conducting the yarn through said preliminary path while the speedof the false-twist spindle is substantially smaller than its normaloperating speed;

thereafter moving said guide point to bring the yarn into its normaloperating path in contact with said heating surface, the movement ofsaid guide point being such that the yarn length between said stretchfeed point and said stretch draw point remains substantially constant;and subsequently increasing the speed of the false-twist spindle up toits normal operating speed. 2. A method as claimed in claim 1 whereinthe yarn is composed of polyethylene terephthalate filaments.

3. In an apparatus for the simultaneous stretching and false-twistcrimping of a yarn, said apparatus including spatially separated feedroll means and draw roll means for stretching a length of yarntherebetween, an elongated curved heating plate for contact with theyarn being stretched and positioned to receive the yarn from said feedroll means during normal operation and a false-twist spindle followingsaid heating plate for imparting a temporary twist to the yarn at apoint preceding said draw roll means, the improvement for threading saidapparatus which comrpises at least one yarn guide means adjacent one endof the elongated heating plate for movement substantially perpendicularto said plate from an open position in which the yarn is maintained freeof contact with the plate to a closed position in which the yarn ismaintained in running contact with said plate, the movement of saidguide means between said open and closed positions being such that theyarn length between said feed roll means and said draw roll meansremains substantially constant.

4. An apparatus as claimed in claim 3 including a plurality of yarnguide means to traverse the yarn back and forth at least twice acrosssaid heated plate, there being at least one of said movable yarn guidemeans at a deflection point of the traversing yarn adjacent one end ofthe heating plate.

5. An apparatus as claimed in claim 4 wherein said heated plate ispositioned at the upper end of the stretch and false-twist crimpingapparatus, the movable yarn guide means being pivotably mounted on anextension rod means for introduction of the yarn first on a lineparallel to the heating plate up to a position at the upper end of theheating plate corresponding to said open position and then in adirection approximately perpendicular to the heating plate through thepivotal movement of the yarn guide means into a position correspondingto said closed position in which the yarn is maintained in runningcontact with the plate.

6. An apparatus as claimed in claim 5 wherein said movable yarn guidemeans is connected by one arm of a two-armed lever to said extension rodmeans, the other arm coacting with a projecting boss of the apparatuscasing to move said yarn guide means into its closed position.

7. Apparatus as claimed in claim 5 wherein said movable yarn guide meansis fixed at the free end of the extension rod which in turn is pivotallyfastened on an axis parallel to the heating plate for moving said yarnguide means through an arc between its open and closed positionsadjacent the upper end of the heating plate.

8. Apparatus as claimed in claim 5 wherein said heating plate ismaintained within a substantially enclosed heating box having insulatedwalls provided with a relatively small opening for entry and withdrawalof said extension rod and the movable yarn guide means associatedtherewith, thereby permitting the yarn to be initially applied to theyarn guide means externally of the heating box.

9. An apparatus as claimed in claim 3 including a plurality of yarnguide means to conduct the yarn back and forth through the Zone of theheating plate around a deflection point at one end of the heating platesuch that the back and forth paths of the yarn are substantiallyparallel to each other, there being provided two movable yarn guide rodsat the other end of the heating plate to carry the parallel running yarnpaths and to provide a movement by at least one of said guide rodsperpendicularly to the heated surface of the heating plate and acombined movement of both rods to maintain said constant yarn length.

10. An apparatus as claimed in claim 3 wherein said at least one movableyarn guide means follows the path of a curve which is approximately theinvolute of the curved yarn contacting surface of the heated plate.

11. A method as claimed in claim 1 wherein said yarn is conductedthrough said preliminary path at a falsetwist spindle speed which ismore than 20 percent smaller than its normal operating speed.

1. A method of threading an apparatus for the simultaneous stretchingand false-twist crimping of a yarn composed of synthetic thermoplasticfilaments wherein the yarn is continuously conducted for stretching in anormal operating path between a stretch feed point and a stretch drawpoint while simultaneously being subjected to a heat treatment by directcontact with an elongated heating surface in said normal operating pathand also imparting a false twist to the heat treated yarn by means of arotating false-twist spindle before the yarn reaches said stretch drawpoint, which process comprises: first threading the yarn from saidstretch feed point to said stretch draw point through said false-twistspindle and also through a movable guide point adjacent one end of saidelongated heating surface, said guide point being initially maintainedin a position such that the yarn runs in a preliminary operating pathwhich is free of contact with said heating surface; then conducting theyarn through said preliminary path while the speed of the false-twistspindle is substantially smaller than its normal operating speed;thereafter moving said guide point to bring the yarn into its normaloperating path in contact with said heating surface, the movement ofsaid guide point being such that the yarn length between said stretchfeed point and said stretch draw point remains substantially constant;and subsequently increasing the speed of the false-twist spindle up toits normal operating speed.
 2. A method as claimed in claim 1 whereinthe yarn is composed of polyethylene terephthalate filaments.
 3. In anapparatus for the simultaneous stretching and false-twist crimping of ayarn, said apparatus including spatially separated feed roll means anddraw roll means for stretching a length of yarn therebetween, anelongated curved heating plate for contact with the yarn being stretchedand positioned to receive the yarn from said feed roll means duringnormal operation and a false-twist spindle following said heating platefor imparting a temporary twist to the yarn at a point preceding saiddraw roll means, the improvement for threading said apparatus whichcomrpises at least one yarn guide means adjacent one end of theelongated heating plate for movement substantially perpendicular to saidplate from an open position in which the yarn is maintained free ofcontact with the plate to a closed position in which the yarn ismaintained in running contact with said plate, the movement of saidguide means between said open and closed positions being such that theyarn length between said feed roll means and said draw roll meansremains substantially constant.
 4. An apparatus as claimed in claim 3including a plurality of yarn guide means to traverse the yarn back andforth at least twice across said heated plate, there being at least oneof said movable yarn guide means at a deflection point of the traversingyarn adjacent one end of the heating plate.
 5. An apparatus as claimedin claim 4 wherein said heated plate is positioned at the upper end ofthe stretch and false-twist crimping apparatus, the movable yarn guidemeans being pivotably mounted on an extension rod means for introductionof the yarn first on a line parallel to the heating plate up to aposition at the upper end of the heating plate corresponding to saidopen position and then in a direction approximately perpendicular to theheating plate through the pivotal movement of the yarn guide means intoa position corresponding to said closed position in which the yarn ismaintained in running contact with the plate.
 6. An apparatus as claimedin claim 5 wherein said movable yarn guide means is connected by one armof a two-armed lever to said extension rod means, the other arm coactingwith a projecting boss of the apparatus casing to move said yarn guidemeans into its closed position.
 7. Apparatus as claimed in claim 5wherein said movable yarn guide means is fixed at the free end of theextension rod which in turn is pivotally fastened on an axis parallel tothe heating plate for moving said yarn guide means through an arcbetween its open and closed positions adjacent the upper end of theheating plate.
 8. Apparatus as claimed in claim 5 wherein said heatingplate is maintained within a substantially enclosed heating box havinginsulated walls provided with a relatively small opening for entry andwithdrawal of said extension rod and the movable yarn guide meansassociated therewith, thereby permitting the yarn to be initiallyapplied to the yarn guide means externally of the heating box.
 9. Anapparatus as claimed in claim 3 including a plurality of yarn guidemeans to conduct the yarn back and forth through the zone of the heatingplate around a deflection point at one end of the heating plate suchthat the back and forth paths of the yarn are substantially parallel toeach other, there being provided two movable yarn guide rods at theother end of the heating plate to carry the parallel running yarn pathsand to provide a movement by at least one of said guide rodsperpendicularly to the heated surface of the heating plate and acombined movement of both rods to maintain said constant yarn length.10. An apparatus as claimed in claim 3 wherein said at least one movableyarn guide means follows the path of a curve which is approximately theinvolute of the curved yarn contacting surface of the heated plate. 11.A method as claimed in claim 1 wherein said yarn is conducted throughsaid preliminary path at a false-twist spindle speed which is more than20 percent smaller than its normal operating speed.